Add ffprobe support
Switch to unix line-endings
Use ffprobe for size/padding calculations
Add deprecation warnings to Metadata object
Update readme
Use ffprobe -print_format instead of -of
Actually use FFPROBE_PATH
Move buildFfmpegArgs to separate file
Index logger messages
Metadata and size refactor

Use ffprobe for internally-needed metadata (only duration actually).
Rewrite size/padding/aspect calculations to use filters instead of manually
computing size and padding from metadata.
Fix scale/pad filter syntax
Round sizes to multiples of 2
Use trunc() instead of -2 for scale filter as -2 is a recent feature
Implement keepPixelAspect
Merge pull request #236 from njoyard/ffprobe

Integrate ffprobe